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RV-1_2n-FUN's avatar
RV-1_2n-FUN
Explorer
Nov 12, 2021

5500 Onan starts then dies, help please

2008 Onan 5500 that I neglected and did not run every month with load since May. Using start switch on the generator, first priming then start the gen. It starts and runs ONLY as long as I hold almost completely closed the butterfly under air filter. If I take pressure off the B-fly opens wide and sounds like gulping air then shuts down with code flashing 36. Reset code, prime and start up and again runs only by holding closed the butterfly. Sprayed plenty of Seafoam in to no avail.

Any ideas of problem???

TIA
  • dougrainer's avatar
    dougrainer
    Nomad
    Nov 12, 2021
    The seafoam did not work. You need to remove the carb fuel bowl and unscrew the needle jet assbly and clean out the 16 holes with regular carb spray. The carb is varnished/gummed up. Doug
  • RV-1_2n-FUN's avatar
    RV-1_2n-FUN
    Explorer
    Nov 12, 2021
    dougrainer wrote:
    The seafoam did not work. You need to remove the carb fuel bowl and unscrew the needle jet assbly and clean out the 16 holes with regular carb spray. The carb is varnished/gummed up. Doug


    Thanks :)

    Will put your suggestion on today's "must do" list.
  • dougrainer's avatar
    dougrainer
    Nomad
    Nov 12, 2021
    A1B00902 wrote:
    check the oil level, Onan will not run if low on oil


    True, but holding the choke butterfly would not override the oil pressure LOPKO. Doug
  • Dirtclods's avatar
    Dirtclods
    Explorer
    Nov 12, 2021
    Seafoam is a fuel treatment it doesn't work well after a problem exist. You gotta have in the tank and if your running lower octane fuels you'll get more **** built up in the carb.
  • Fisherman's avatar
    Fisherman
    Explorer
    Nov 12, 2021
    Octane has absolutely no effect on the amount of crud building up in a fuel system.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Nov 12, 2021
    You sprayed seafoam into the throat of the Carb.
    But from your description I'd say it needs carb cleaned.
    it is SLIGHTLY possible that adding seafoam to the tank might help
    But I think Disassembly and cleaning is in order.

    NOTE: This is not the only possible issue.
  • RV-1_2n-FUN's avatar
    RV-1_2n-FUN
    Explorer
    Nov 12, 2021
    Broke down the carb today and the inside looked as clean as the day it was assembled. Didn't have any cleaner so put Seafoam through everything then reassembled and WHAM-BAM it ran but only for 5 minutes.

    Same as before r.e.-shutting down, so held butterfly and it ran great.

    THANKS for the replies.
  • RV-1_2n-FUN's avatar
    RV-1_2n-FUN
    Explorer
    Nov 24, 2021
    Generator starts better than before then only runs for 4 minutes and dies. Checked pump with hose disconnected and pressure seems good so totally flustered and figure it's time for $$$$ and a pro.
  • Skibane's avatar
    Skibane
    Explorer II
    Nov 24, 2021
    It really sounds like you were on the right track with cleaning the carb, but didn't go far enough.

    Did you thoroughly clean the small passages? Typically, it takes a piece of small-diameter wire to rod them out.

    Also, Sea Foam is not a particularly good substitute for carb cleaner.

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